Birth defect risk from high dose of epilepsy drugs

Women who take four common epilepsy drugs are at greater risk of having a baby
born with birth defects, research suggests.

The first comprehensive study in the area found that pregnant women who are prescribed high doses of the medication to control seizures are particularly at risk of having a baby with spina bifida, heart problems or cleft palate.

Academics found that 230 babies in a study of almost 4,000 pregnancies of women with epilepsy led to birth defects, but point out that the vast majority had “perfectly healthy children”.

W Allen Hauser from Columbia University, New York, said: “The findings are important to the clinician treating people with epilepsy because they provide specific information not only on the drug but also on the dose.

“It is easy to recommend against use of a specific drug (valproic acid, for instance) because of a higher risk of malformations, but if seizure control is not possible with alternative therapeutic regimens, such recommendations are difficult to implement.”

Up to 0.7 per cent of pregnancies are in women who have epilepsy but most need to keep taking antiepileptic drugs in case they suffer a fit that harms themselves and their unborn child.

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It has long been feared that the drugs may lead to birth defects and later problems with their babies’ development but previous studies did not provide an accurate comparison of the possible risks of different drugs at various dosages.

In a new study, published in the Lancet Neurology journal on Monday, researchers from the Karolinska Institute in Sweden analysed figures on 3,909 pregnancies among women with epilepsy recorded in a database called EURAP.

Looking at four drugs at a variety of doses, they found the fewest birth defects (2 per cent) were among children born to women who had taken less than 300mg a day or a drug called Lamotrigine.

By comparison, they found “significantly increased” risk among those who took more than 400mg a day carbamazepine (between 5 per cent and 9 per cent rate of major congenital malformations), and those who took valproic acid and phenobarbital at all doses. Among the 99 women who took more than 1,500mg a day of valproic acid, 24 per cent had babies with birth defects.

“Our results show that dose selection is as crucial as the choice of the drug,” the researchers conclude.

They also found that the risk of defects was four times greater for children with a parental history of major congenital malformations.